Telephone-exchange system.



A. E. LUNDELL 6L F. A. SEARN.

TELEPHONE EXCHANGE SYSTEM.

APPLxcATIoN F1110 nov.2s,1917.

1,294,498. Patented Feb.18,1919.

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A. E. LUNDELL & F. A. STEARN.

TELEPHONE EXCHANGE SYSTEM.

APPucATmN man Nov. 2e, 1911.

pQQQS. Patented Feb. 18, 1919.

4 SHEETS-SHEET 2.

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A. E. LUNDELL & F. A. STEARN.

TELEPHONE EXCHANGE SYSTEM.

APPucATloN man Nov. 2s. |911;

1,29A98, y Patented Feb.1s,1919.

4 SHEETS-SHEET 3.

A. E. LUNDELL 6L F. A. STEARN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV.26. 1917.

ALBEN E. LUNDELL, or NEW YORK, N, Y., AND FRANKLIN A. s'rE'AEN, 0EPATENSCN, NEW JERSEY, .assreNons To WESTERN ELECTRIC COMPANY,INCORPORATED, CE NEW Yoan, N. Y., s CORPORATION or NEW Yom. l

TELEPHONE-EXCHANGE SYSTEM.

To all whom t may concern:

Be it known that we, ALBEN E. LUNDELL and FRANKLIN A. STEARN, citizensof the United States, residing at New York, in the county of Bronx andState of New York, and at Paterson, in the county of Passaic and Stateof New Jersey, respectively, have invented certain new and usefulImprovements in Telephone-Exchange Systems, of which the following is afull, clear, concise, and exact description.

This invention relates to automatic telephone systems, and has for itsobject the provision of improved means for controlling the disconnectionof various switching devices thereof which are used for interconnectingtelephone lines for conversation.

lt is the object of this invention to provide improved means forcontrolling the operation of the automatic switch mechanism or selectorswitches to cause their release after starting, but before completingtheir operation to interconnect subscribers telephone lines.

The invention readily be adapted to various types of telephone exchangesbut the present embodiment is especially designed for use insemi-auton'latic systems wherein the sending apparatus is located at thecentral oiice and arranged for actuation by an operator in accordancewith instructions recei ved from a calling subscriber. In the systemdisclosed the initial connection between the operator and the callingline is made by the operator by inserting a plug, at the answering endof a cord circuit, into the jack of the calling line. The outgoing endot' each cord terminates in a selector switch` and sending mechanism istemporarily associated with the cord circuit while connection is beingestablished, for the purpose of controlling the operation of this andother switches by means of which the connection between subscriberslines is established. These switches are of the type disclosed in Patent1,123,696, issued Jan. 5, 1915, to E. B. Craft and J. N. Reynolds.Associated with each cord circuit and under the control of the operator,an arrangement is provided whereby under certain conditions the switcheswhich are used in establishing a connection may be returned to theirnormal position before a complete connection is established.

Specification of Letters Patent.

A feature ofthe invention is an arrangement whereby this restoring meansmay be operated during a period in which the selector switches are beingselectively operated.

This feature is accomplished by holding ythe fundamental `circuit closedupon the depression of a key by the operator, thereby causing theswitch, which is being operated, to move to its uppermost position,which positlon 1s known as tell-tale. The sequence switch associatedwith said switch will then be rotated into talking` position. The switchwhich is being operated, is then returned to normal by the disconnectionof the district selector, which is released when the tell-tale positionof the switch under selection is reached.

The movement of the selector mechanism may thus, be checked before ithas completed the desired connection and be caused immediately to returnto normal. Thus in casev the operator has made a mistake in manipulationof the sending apparatus, she is enabled to start a new connectionimmediately. Hereto-fore, after the first selector' switch had beenselectively operated, the connection could not be released until afterthe last series of impulses had been sent from the sending apparatus.

ln the drawing, Figure l shows circuits and apparatus which are directlyassociated with a cord circuit terminating in a selector switch, thisbeingxlrnown as the district switch; Fig. 2 shows the circuitsassociated with an incoming selector switch; Fig. 3 shows the circuitsassociated with a final selector switch; and Fig. 4 shows the circuitsassociated with a sender controlling mechanism and a cord nder.

The operation of the system will now be described. First, a call will betraced from a calling to a called subscriber and then the means forwiping out a call will be de scribed. This last description will onlyrefer to the operation of the system after one of a train of switcheshas been operated and is in a position to allow the operation of theremaining switches of the train, since this invention relates only tothe release of the switches at this particular period of the operationof the system.

Then the subscriber at substation A removes his receiver from the hook,a circuit is completedfrom grounded battery, lett-v,

Patented Feb.' 18, 1919.

Application filed November 26, 1917. Serial No. 204,081. i

hand winding of relay 101, outer armature and back contact of relay 102,apparatus of substation A, back contact and inner armature of relay 102,right-hand winding of relay 101, to ground. Relay 1011 becomes energizedand closes a circuit for lamp 108.

rEhe operator seeing the lighted lamp inserts the plug 104 lintoV thejack 105 associated with the calling line. A circuit is then completedfrom grounded battery, Winding of cutoill relay 102, sleeve of jack 105,sleeve of plug 104, winding of relay 106, to ground. Relay 102 isenergized and causes the de'e'nergization of relay 10'1 in a well-knownmanner. Relay 106 becomes energized and closes a circuit from groundedbattery, power magnet of sequence switch 100, upper lett-hand contact ofsequence switch spring 107, front contact and arma* ture of relay 106,to ground, for moving the sequence switch 100 out ot position 1 and intoposition 2.

1n position 2, a circuit is closed from grounded battery, winding ofrelay 401, lower contact of sequence switch spring 402, conductor 403,lett-hand contact of sequence switch spring 108, to ground. Relay 401 byattracting its lett-hand armature closes a circuit from groundedbattery, power magnet ot1 sequence switch 400, upper right-hand contactof sequence switch sprin g 404, left-hand armature and front contact ofrelay 401, to ground, for moving the sequence switch 400 out of position1 and into position 2. as soon as the sequence swiich 400 reachesposition 1-1/2 a locking circuit for relay 401 maintains this relayenergized, this circuit being traced from grounded battery-winding ofrelay 401, right-hand armature and front Contact of relay 401, up-

er contacts or sequence switch spring 402` hack contact ad right-handarmature of relay 405, to ground.

1n position 2 of sequence switch 400, a circuit is closed from groundedbattery, winding of updrive magnet 406, contact oiI sequence switchspring 407, front contact and left-hand armature of relay 401, toground. Under the control of the updrive magnet 406, the brushes of thecord tinder are moved upward. As soon as the brush 408 engages terminal409, a circuit is closed from grounded battery, winding of relay 405,left-hand Contact of sequence switch spring 411, brush 408, terminal409, conductor 410, lower right-hand contact of sequence switch spring108, to ground. -Relay 405 becomes energized and closes a lockingcircuit for itself from grounded battery, winding ot relay 405,right-hand Contact of sequence switch spring 411, left-hand armature andfront contact of relay 405, brush 412, terminal 413, conductor 414,upper contact oit sequence switch spring 108, to ground, Relay 405 byattracting its right-hand ar- Langues mature opens a branch ot theenergizing circuit of relay 401, but this relay is held energized untilthe brushes are accurately centered due to a circuit being closed fromgrounded battery, windingof relay 401, righthand armature and frontcontact of relay 401, conductor 415, conducting segment of commutator416, commutator brush 417, to ground. As soon as the brushes areaccurately centered en the terminals, the brush 417 engages an insulatedsegment of the commutator 416, thus causing the relay 401 to bedenergized and open the energizing circuit of the updrive magnet 406.The denergization of relay 401 also closes a circuit from groundedbattery, power inagnet of sequence switch 400, upper left-hand contactof sequence switch spring 404, back Contact and left-hand armature ofrelay 401, to ground, for moving the sequence switch 400 out of position2 and into position 3. 1n position 3, a circuit is closed from groundedbattery, power magnet of sequence switch 490, lower contact of sequenceswitch spring 492, contact of sequence switch spring 418, to ground, formoving the sequence switch 400 out of position 1 and into position 3.

At the time relay 106 is energized, by the insertion of the plug 104into the jack 105, a circuit is also completed from grounded battery,power magnet of listening key sequence switch 175, contact of sequenceswitch spring 176, front contact and armature of relay 106, to ground`for moving the listening key sequence switch out of position 1 and intoposition 5. As Isoon as the listening key sequence switch reachesposition 4, the operators telephone sct is connected to the cordassociated with the plug 104, thereby enabling the operator to ascertainthe desired number from the calling subscriber. 14s soon as she obtainsthis number', she sets it up upon her key board. As is well known in theart, the operator has one row of oiiice keys and four rows or' digitkeys, and by pressing one key ot each row. six sets of impulses aretransmitted due to translation. 1n order, however, to simplify thedisclosure and description in the present invention. a key for each setof impulses is shown, it being assumed that there are two oihce keysinstead of one.

1t will be assumed that the operator depresses the No. 1 key in theoflice tens row- No. 2 key in the oliice units row, No, 0 key in thethousands row, No. 2 key in the hundreds row, No. 1 key in the tens row,and the No. 2 key in the units row. As soon as she has set up thisnumber she depresses the start key 491` thereby completing a circuitfrom grounded battery, power magnet of sequence switch 400, lowerlefthand contact of sequence switch spring 404. key 491, to ground, formoving .sequence switch 40G-out of position 3 and into position 8. Acircuit is also completed at this time from grounded battery, powermagnet ot' sequence switch 490, upper right-hand contact of sequenceswitch spring 492, key 491 to ground, for moving the sequence switch 490out of position 3 and into position 6.

As soon as the sequence switch 490 reaches position 6, the fundamentalcircuit is closed :t'rom grounded battery, winding of relay 109, lowerright-hand contact of sequence switch spring 110, conductor 111,terminal 419, brush 420, right-hand armature and back contact of relay421, contact of sequence switch spring 493, outer armature and backcontact of counting'. relay 0, winding of stepping relay 494, brush 422,terminal 423, conductor 424, upper left-hand contact of sequence switchspring 112, to ground.

The relay 494 becomes energized, and by attracting its armature,completes a Circuit from grounded battery, winding of counting relay 1,armature and back contact of counting relay l', conductor 497, No. 1 keyof the oiiice tens row, lower contact of sequence switch spring 496,armature and front contact of relay 494, to ground. Counting relay No. 1by attracting its armature closes a circuit from grounded battery,windings of counting relays 1 and 1, armature and front contact ofcounting relay 1, upper right-hand contact of sequence switch spring485, to ground. Counting relay 1', however, does not become energized atthis time, due to the shunt around its winding which is closed at thearmature and front contact of the stepping relay 194.

Relay 109 also becomes energized at the time the fundamental circuit isclosed and closes a circuit from grounded battery, power magnet ofsequence switch 100, lower contact of sequence switch spring 113, right`hand armature and front Contact of relay 109, to ground, for moving thesequence switch 100 out of position 2 and into position 3. While thesequence switch is mov-` ing from position 2 into position 3, relay 109is held energized over a locking circuit extending through its left-handarmature and front contact and the lower left-hand contact of sequenceswitch spring 110, to

ground over the circuit previously described. In position 3 a circuit isclosed from grounded battery, winding of updrive magnet 114, uppercontact of sequence switch spring 115, front contact and righthandkarmature of relay 109, to ground. Under the control of the updrivemagnet 114, the brush rod 116, carrying the line brushes 117, 118 and119 and commutator brushes 120 and 121` is moved upward. As soon as thecommutator brush 120 engages the first conducting segment of thecommutator 122, a shunt circuit is closed around the stepping relay 494,this circuit being traced from grounded battery, winding of relay 109,lett-hand armature and front contact of relay 109, lower left-hand andupper right-hand contacts of sequence switch spring 110, conductingsegment of commutator 122, commutator brush 120, to ground. Steppingrelay 494 denergizes and opens the shunt around the counting relay 1which becomes energized. As soon as the commutator brush 120 engages therst insulated segment of the commutator 122, the stepping relay 494 isagain energized and a circuit for the 0 counting relay is completedthrough the armature and front contact of the No. 1 counting relay. The0 counting relay becomes energized and closes a circuit for the 0counting relay which, however, does not become energized on account ofthe shunt around its winding which is closed by the armature and frontcontact of the stepping relay 494. As soon as the commutator brush 120engages the second conducting segment of the commutator 122, thestepping relay 494 is again deenergized thereby causing the-energization of the 0 counting relay. The 0 counting relay byattracting its inner armature closes a circuit from grounded battery,power magnet of sequence switch 490, inner armature and front contact ofthe 0 counting relay, left-hand contact of sequence switch spring 485,to ground, for moving the sequence switch 490 out of'position 6 and intoposition 8. The relay 0 by attracting its outer armature opens thefundamental circuit, but the relay 109 is held energized until theeommutator brush 120 engages the second insulated segment of thecoinmutator 102, due to the shunt circuit previously described. As soonas the commutator brush engages this insulated segment, relay 109denergizes and opens the circuit of the 11p-- drive magnet 114. Brushes117, 118 and 119 are now accurately centered upon the first set ofterminals of the second group in the district terminal bank. The denergization of relay 109 also closes a circuit from grounded battery,power magnet of sequence switch 100, upper left-hand contact of sequenceswitch spring 113, right-hand armature and back contact of relay 109, toground, for moving the sequence switch 10'0 out of position 3 and intoposition 6.

In position 6 a circuit is closed from grounded battery, left-handwinding of relay 123, upper right-hand and lower left'hand contacts ofsequence switch spring 124, to ground. Relay 123 by attracting its outerright-hand armature completes a circuit from grounded battery, powermagnet of sequence switch 100, lower right-hand contact ot sequenceswitch spring 125, outer right hand armature and Jfront contact of relayL recati-ee 123, to ground, for moving the sequence switch 100 out ot'position 6 and into position 7. It the trunk with which the brushes 117,113 and 119 are in engagement, is busy, ground will be connecteddirectly to the test terminal thereof, so that when relay 123 becomesenergized it closes a locking circuit for itselt' from grounded battery,right-hand winding of relay 123, inner right-hand armature and frontcontact of relay 123, conductor 126, test brush 119, test terminal 127,to ground. The relay 123 will then be energized when the sequence switch100 reaches position 7 and a circuit will be closed from groundedbattery, winding ot' updrive magnet 114, lower contact of sequenceswitch spring 115, outer rightfhand armature and front contact of relay123, to ground. Under the control oit the updrive magnet 114, thebrushes 117, 118 and 119 are moved upward until the test brush 119engages the test terminal 127 of an idle trunk, at which time thecircuit through the right-hand winding ot re lay 123 will not receivesuiicient current to hold its armatures, due to the ground beingconnected to the test terminal through a high resistance, this circuitbeing traced from the test terminal 127, conductor 273, resistance 274,to ground. A. circuit, however, will be closed for maintaining the relay123 energized until the brushes are accurately centered upon theterminals ot this idle trunk, this circuit being traced from groundedbattery, lett-hand winding ot' relay 123, upper contacts of sequenceswitch spring 124, front Contact and left-hand armature ot relay 123,conductor 128, conducting segment of commutator 129, commutator brush121, to ground. As soon as the brushes are accurately centered thecommutator brush 121 will engage an insulated segment of the commutator129, thereby causing the retraction of the armatures ot' relay 123.Relay 123 by retract-ing its outer right-hand armature opens the circuitot the updrire magnet 114 and closes a circuit from grounded battery,power magnet of sequence switch 100, lower left-hand contact of sequenceswitch spring 125, outer right-hand armature and back Contact of relay123, to ground. for moving the sequence switch 100 out ot position 7 andint-o position 11. When the sequence switch 100 reaches position 6-1/'2and relay 123 is denergized, `ground is connected directly to the testterminal 127, to cause the selected trunk to test busy at the multipleytest terminals thereof. this circuit being traced from ground. upperright contact ot sequence switch spring 112, inner right-hand armatureand back Contact ot' relay 123 and brush 119 to test terminal 127.

As soon as the sequence switch 100 reaches position 11 and the sequenceswitch 490 reaches position 8, the fundamental circuit is again closed,this circuit now being traced from grounded battery, upper contacts ofsequence switch spring 201, Contact 227 winding of relay 202, lower andupper lefthand contacts of sequence switch spring 203, conductor 229,resistance 228, conductor 205, terminal 131, brush 117, lower Contact ofsequence switch spring 132, conductor 111, terminal 419, brush 420,right-hand armature and back contact ot relay 421, contact of sequenceswitch spring 493, outer aru'iature and back contact of counting relay0, winding of stepping relay 494, brush 422, terminal 423, conductor424, upper contact of sequence switch spring 133, brush 118, terminal130, conductor 206, resistance 207, upper left-hand Contact of sequenceswitch spring 208, winding ot' relay 209, lower contact of sequenceswitch spring 210, to ground. Relays 202 and 209 are energized and closea circuit from grounded battery, power magnet of sequence switch 200,lower Contact of sequence switch spring 211, armature and front contactof relay 209, upper contact ot sequence switch spring 212, front contactand right-hand armature of relay 202, to ground, for moving the sequenceswitch 200 out of position l and into position 2.

1n position 2, relay 202 is still maintained energized due to a circuitbeing closed from grounded battery, upper contacts ot sequence switchspring 201, contact 227, winding of relay 202, lower right-hand contactof sequence switch spring 230, left-hand armature and front contact ofrelay 202, upper contacts of sequence switch spring 203, to ground, overthe fundamental circuit previously described. A circuitl is nowcompleted from grounded battery, winding of updrive magnet 217, lowercontact of sequencev switch spring 213, right-hand armature and front,contact otl relay 202 to ground. Under the control of the updrive magnet217, the line brush sets and the commutator brushes 231, 232, 233 and234 are moved upward. When the fundamental circuit is closed in themanner just described, the stepping relay 494 is energized and completesa circuit from grounded battery, winding of counting relay 2, armatureand back contact of counting relay 2, conductor 498, No. 2 key of theoffice units row, upper right-hand contact of sequence switch spring496, armature and front contact ot stepping relay 494, to ground. As thecommutator brush 231 moves upward, it engages the conducting segments ofthe commutator 235. Each time the commutator brush 231 engages one ofthese segments, a circuit is closed from grounded battery, uppercontactsot sequence switch spring 201, Contact 227, winding of relay202, lower righthand Contact of sequence switch spring 230, lett-handarmature and front contact of relay 202, conductor 246, upper contactsot sequence switch spring 214, conducting segments of commutator 235,commutator rush 231, lower right-hand contact of sequence switch spring220, to ground. This circuit places a shunt around the relay 494 whichdenergizes and operates the countm'g relays in thesame manner as abovedescribed. The commutator brush y231 continues to move upward until itengages the third conducting segment, at which time the 0 counting relaywill be energized. This relay by-l attracting its inner armaturecompletes a circuit from grounded battery, power magnet of sequenceswitch 490, inner armature and front Contact of counting relay 0', upperleft-hand contact of sequence switch spring 485, to ground, for movingthe sequence switch 490 out of position 8 and into position 10. As soonas the sequence switch 490 leaves positionl 8 the counting relays aredeenergized, due to the 'opening of their locking circuits at the upperright-hand contact of sequence switch spring 485. Counting relay 0 byattracting its outer armature opens the fundamental circuit and opensthe original energizing circuit of relay 202. As soon as the commutatorbrush 231 engages the third insulated segment of the commutat-or 235,relay 202 becomes denergized and by retracting its right-hand armatureopens the circuit of the updrive magnet 217, and closes a circuit fromgrounded battery, power magnet of sequence switch 200, upper right-handcontact of sequence switch spring 211, righthand armature and backcontact of relay 202, to ground, for moving the sequence switch 200 outof position 2 and into position 3.

As soon as the sequence switch 200 reaches position 3 and sequenceswitch 490 reaches position 10, the fundamental circuit is againestablished, causing the energization of the relays 202 and 494. Relay494 by attracting its armature completes a circuit from groundedbattery, winding of counting relay 0, conductor 499, No. 0 key ofthethousands row, upper left-hand contact of sequence switch spring 496, toground. Relay 202 by attracting its right-hand armature closes a circuitfrom grounded battery, power magnet of sequence switch 200, upperleft-hand contact of sequence switch spring 211, front contact andright-hand armature of relay 202, to ground. for moving the sequenceswitch 200 out of position 3 andinto position 4. Relay 202 byattracting. its lefthand armature closes a locking circuit for itself aspreviously described.

In position 4 of sequence switch 200, a circuit is completed fromgrounded battery, winding of updrive magnet 217, lower contact ofsequence switch spring 213, righthand armature and front contact ofrelay 202, to ground. Under the control of the updrive magnet the lineand commutator brushes are again moved upward. As the brush rod 236moves upward the third set of brushes is tripped due to the energizationof the trip magnet 216, this energizing circuit being traced fromgrounded battery, winding of trip magnet 216, upper contact of sequenceswitch spring 215. to ground. As soon as the commutator brush 232 e11-gages the first conducting segment of the commutator 237, a circuit isclosed from grounded battery, upper contacts of sequence switch spring201, contact 227, winding of relay 202. lower right-hand contact ofsequence switch spring 230, left-hand armature and front Contact ofrelay 202, upper and lower right-hand contacts of sequence switch spring203, conductor 238, conducting segment of commutator 237, brush 232,lower right-hand contact of sequence switch spring 220, to ground. Thiscircuit shunts out the stepping relay 494, which in turn causes theenergization of the 0 counting relay in the same manner as previouslydescribed. The 0 counting relay by attracting its inner armaturecompletes a circuit from grounded battery, power magnet of sequenceswitch 490, inner armature and front contact of 0 counting relay,left-hand contact of sequence switch spring 485, to ground, for movingsequence switch 490 out of position 10 and into position 12. The 0counting relay by attracting its outer armature opens the fundamentalcircuit, thereby allowing the relay 202 to denergize as soon as thecommutator brush 232 engages an insulated Segment of the commutator 237.Relay 202 by retracting its right-hand armature opens the energizingcircuit of the updrive magnet 2.17 and closes a circuit from groundedbattery, power magnet of sequence switch 200, upper right-hand contactof sequence switch spring 211, back contact and right-hand armature ofrelay 202, to ground, for moving the sequence switch 200 out of position4 and into position The brushes 223, 224 and 225 are now in engagementwith the tirstset of terminals in the selected group.

In position 5 of sequence switch 200 a circuit is closed from groundedbattery. lower contact of sequence switch spring 218, lefthand windingof relay 219, upper and lower right-hand contacts of sequence switchspring 220, to ground. Relay 219 by attracting its lett-hand armaturecloses a circuit from grounded battery, power magnet of sequence switch200, upper contact of sequence switch spring 239. left-hand armature andfront contact of relay 219, to ground, for moving the sequence switch200 out of position 5 and into position 6- If the brush 223 is inengagement with the terminal of a busy trunk. a circuit is now closedfrom grounded battery, right-hand winding of relay 219, lower contact ofsequencevswitch spring 221, right-hand armature and front contact ofrelayr 219, resistance 222, brush 223, to ground, through the testterminal 241 of the busy trunk. Relay 219 is thereby held energized inposition 6 and completes a circuit from grounded battery, winding ofupdrive magnet 217, 4upper contact of sequence switch spring 213,left-hand armature and front contact of relay 219 to ground. Under f thecontrol of the updrive magnet 217, the

brushes are moved upward over the contacts of the selected group oftrunks until the test brush 223 engages the test terminal of an idletrunk, at which time the relay 219 denergizes, duc to the absence ofground on the test terminal. Relay 219 is held energized, however, untilthe brushes are accurately centered on the terminals of the idle trunk,due to a circuit being closed from grounded battery, lower contact ofsequence switch spring 218, left-hand winding of relay 219, conductingsegment of commutator 240, commutator brush 234, lower left-hand contactof sequence switch spring 220, leftlia-ud armature and front contact ofrelay 219, to ground, As soon as the brushes are accurately centered onthe terminals of the idle trunk, the conimutator brush 234 engages aninsulated segment of the commutator 240, thus causing the denergizationof relay 219. Relay 219 by retracting its lefthand armature opens thecircuit of the updrive magnet 217 and closes a circuit from groundedbattery, power magnet of sequence switch 200, lower contacts of sequenceswitch spring 214, left-hand armature and back Contact of relay 219 toground, for moving the sequence switch 200 out of position G and intoposition 7. As soon as the sequence switch reaches lposition 6-3/4,ground is connected to the test terminal 241 of the selected trunk andcauses this trunk to test busy, this circuit being traced from testterminal 241, brush 223, resistance 222, lower contact of sequenceswitch spring 244, to ground.

1n position 7, a circuit is closed from grounded battery, uppercont-acts of sequence switch spring 201, contact 227, winding of relay202, left-hand Contact of sequence switch spring 230 to ground. Relay202 by attracting its right-hand armature completes a circuit fromgrounded battery, power magnet of sequence switch 200, upper left-handcontact of sequence switch spring 211, right-hand armature and frontcontact of relay 202, to ground, for moving sequence switch 200 out ofposition 7 and into position 9. Relay 202 by attracting its lefthandarmature completes a locking circuit for itself, this circuit beingtraced from grounded battery, upper contacts of sequence switch spring201, contact 227, winding of relay 202` right-hand contact of sequenceswitch spring 230` left-hand armature and front contact of relay 202,conreeaaes ductor 246, right-hand contact of sequence switch spring 247,conductor 248, brush 2247 fterminal 242, conductor 301, lower left-handand upper right-hand contacts of sequence switch spring 302, resistance303, yto ground. Relay 202 is lleld energized over this circuit untilthe sequence switch 300 leaves position (i.

As soon as the sequence switch 200 reaches position 9 and the sequenceswitch 490 rear-.lies position 12, a circuit is completed from groundedbattery, winding of relay 304, lower left-hand Contact of sequenceswitch spring 305, conductor 306,'terminal 243, brush 225, conductor249, upper lefthand contact. of sequence switch spring 250, resistance228, over the fundamental circuit previously' described, -to ground,through the resistance 207 and the contact of sequence switch spring251. Relays 304 and 494 become energized. Relay 494 completes a circuitfrom grounded battery, winding of counting relay No. 2,l armature andback contact of counting relay No. 2f, conductor 439, No. 2 key of thehundreds row, lower left-hand contact of sequence switch spring 495,armature and front contact of relay 494, to ground. Counting relay No. 2becomes energized and closes a circuit for counting relay No. 2 in thesame manner as above described.

Relay 304 by attracting its right-hand armature closes a locking circuitfor itself from grounded battery, winding` of relay 304. right-handarmature and front contact of relay 304, lower right-hand Contact ofsequence switch spring 305, to ground, over the fundamental circuit.Relay 304 by attracting its left-hand armature completes a circuit fromgrounded battery, winding of relay 307, lower left-hand and upperright-hand contacts of sequence switch spring 303, left-hand armatureand front Contact of relay 304 to ground. Relay 307 by attract-ing itsright-hand armature completes a locking circuit for itself fromgroundedbattery, winding of relay 307, right-hand armature and frontcontact of relay 307, resistance 309, conductor 310, terminal 241, brush223, resistance 222, lower 115 contact of sequence switch 244, toground. Relay 307 by attracting its left-hand armature closes a circuitfrom grounded battery, power magnet of sequence switch 300, upperright-hand Contact of sequence switch spring 12o 311, left-hand armatureand front Contact of relay 307, to ground, for moving the sequenceswitch 300 out of position l and into position 2.

1n position 2 a circuit is completed from 12e grounded battery, windingof updrive magnet 312, lower contact of sequence switch spring 313,conductor 314, left-hand arma- =ture and front contact of relay 304, toground. Under the control of the updrive 130 magnet 312 the line brushsets 315, 316 and 317, the commutator brushes 318, 319 and 320 are movedi-ipward.v As soon as the commutator brush 319 engages the firstconducting segment of the commutator 321, a circuit is completed fromgrounded battery,

winding of relay304, right-hand armature tinue 'to move upward until thecountingl relay 0 is energized, at which time the fundamental circuit isopened. Relay 304 then becomes denergized as soon as the commutator 319engages an insulated segment ot' the commutator 321. Relay 304 byretracting its left-hand armature opens the circuit ot' the updrivemagnet 312 and completes a circuit from grounded battery, power magnetof sequence switch 300, lower right-hand and upper left-hand contacts ofsequence switch spring 308, left-hand armature and back contact of relay304, to ground, for moving the sequence switch 300 out of position 2ergization of counting relay 0 also completes a circuit from groundedbattery, power magnet of sequence switch 490, inner armature and frontcontact of counting rela)r 0. lett-hand contact of Sequence switchspring 485, to ground, for moving the sequence switch 490 out ofposition `12 and into position 14.

As soon as the sequence switch 300 reaches position .3 and the sequenceswitch 490 reaches position 14, the fundamental circuit is againestablished, causing the energization of relays 304 and 494. Relay 494by attracting its armature completes a circuit from grounded battery,winding of counting relay 1, armature and back contact ot counting relay1', conductor 48T, No. 1 lrey of thc tens row, lower right-hand contactof scquence switch spring 495, armature and front contact otl relay 494,to ground. Counting relay No. 1. by attracting its armature. closes acircuit through counting relay No. 1, in the same manner as abovedescribed. lelay 304 b v attracting itsI right-hand armature closes thelocking circuit for itself as previously described. and by attraitingits left-hand armature closes a circuit from grounded battery. sequenceswitch 300. lower and upper right-hand contacts of sequence switch 308,lett-hand armature and front contact of relay 304. to ground, formoving` the sequence switch 300 out of position 3 and into position 4,and as soon as sequence and into position 3. The enswitch 300 leavesposition 4, the circuit of the updrive magnet 312 is closed, aspreviously described. Under the control of the updrive magnet 312, thebrushes are again moved upward. The third set of brushes is tripped atthis time, since the trip magnet 324 is energized due to a circuitclosed from grounded battery, winding of trip magnet 324, contact ofsequence switch spring 4325, to ground. As soon as the commutator brush320 engages the first conducting segment of commutator 327, a circuit isclosed from grounded battery, winding of relay 304, right-hand armatureIand front cont-act of relay A304, lower right-hand contact of sequenceswitch spring 305, lower contact of sequence switch spring 322,conducting segment of comn'uitator 327, commutator brush 320, lowercontact of sequence switch spring 323, to ground. This circuit closes ashunt around the stepping relay 494, which deenergizes and allows thecounting relay 1 to energize. As the brushes move upward the countingrelays are actuated in the same manner as above described, and until thccounting relay 0 is again energized. Counting relay 0 by attracting itsinner armature completes a circuit from grounded battery, power magnetof sequence switch 490, inner armature and front contact of countingrelay 0, left-hand contact of sequence switch spring 485, to ground, formoving the sequence switch 490 out of position 14 and into position 16.Counting relay 0 by attracting its outer armature again opens thefundamental circuit, thereby causing the de'e'nergization of relay 304.as soon as the commutator brush 320 engaUes an insulated segmentofcomlnutator 32. Relay 304 by retracting its left-hand armature opens thecircuit of the updrive magnet 312, and closesa circuit from groundedbattery, power magnet of sequence switch 300, lower right-hand and upperleft-hand contacts of sequence switch spring 308, lett-hand armature andback contact of relay 304. to ground. tor moving the sequence switch 300out of position 4 and into position 5.

As soon as they sequence switch 300 reaches position 5 and the sequenceswitch 490 reaches position 16, the fundamental circuit is againestablished, causing the energization of relays 304 and 494. Relay 494 bv attracting its armature completes a circuit from grounded battery,winding of counting relay 2, armature and back contact of counting relay2, conductor 486, No. E2 key of the units row, upper contact ot'sequence switch spring 495, armature and Yl'ront contact of relay 494,to ground. Counting relay No. 2 lby attracting its armature closes acircuit for counting rela-y No. 2. in the same manner as abovedescribed. Relay 304 by attracting its right-hand armature closes thelocking circuit for itself, previousl described, and by attracting itslefthan armature completes a circuit for moving the sequence switch 300out of position 5 and into position 6, and as soon as the sequenceswitch reaches position 6 a circuit is closed from grounded battery,winding ot' slow-speed updrive magnet 328, upper contact of sequenceswitch spring 313, left-hand armature and t'ront contact of relay 304,to ground. Under the control ot magnet 328, the selected brush set ismoved upward. As the brushes move upward, the brush 319 by engaging thecommutator 321. actuates the counting relays in the same manner as abovedescribed. As soon as the counting relay 0 is energized, a circuit iscompleted from grounded battery, power magnet of sequence switch 490.inner armature and front contact otl counting relay 0', left-handcont-act ofsequence switch spring 485, to ground. for moving thesequence switch 490 out of position 16 and into position 1. As soon asthe sequence switch 490 reaches position 1, a circuit is closed fromgrounded battery, power magnet of sequence switch 100, lower Contact otsequence switch spring 107, conductor 134, terminal 4.31, brush 432,contact of sequence switch spring 433, upper Contact ot sequence switchspring 484, to ground, for moving the sequence switch 100 out ofposition 11 and into position 16` In position 1 of sequence switch 490,a circuit is also closed :trom grounded battery, winding of downdrivemagnet 428 of the cord finder, contact of sequence switch spring 429,contact of sequence switch spring 483, to ground. Under the control ofthe downdrive magnet 428, the brushes of the cord finder are returned totheir normal position. As soon as the commutator brush 417 reaches itsnormal position, a circuit is closed from grounded battery, power magnetof sequence switch 400, lower right-hand contact of se` quence switchspring 404, conductor 430, conducting segment 451, commutator brush 417,to ground, for moving the sequence switch 400 out ot position 8 and intoposition 1.

`When the fundamental circuit was opened by the energization ot countingrelay 0, relay 304 became denergized as soon as the commutator brush 319engaged an insulated segment of the commutator 321. Relay 304 byretracting its lett-hand armature opens the circuit of the updrivemagnet 328 and closes a circuit from grounded battery, power magnet ofsequence switch 300, lower righthand and upper lett-hand contacts ofsequence switch spring 308. lett-hand armature and back contact of relay304, to ground, for moving the sequence switch 300 out of position 0 andinto position 7. The brushes 315, 316 and 317 are now in engagement withthe terminals ot the desired line.

As soon as the sequence switch 300 leaves recense position 6, theholding circuit of relay 202 is opened at the upper right-hand contactof sequence switch spring 302. The deenergization of relay 202 closes acircuit from grounded battery, power magnet of sequence switch 200,upper right-hand contact of sequence switch spring 211, righthandarmature and back Contact of relay 202, to ground, for moving thesequence switch 200 out of position 9 and into position 10. A circuit isnow closed from grounded battery, lower lett-hand Contact of sequenceswitch spring 252, winding of relay 253, upper left-hand winding ofrepeating coil 254, conductor 205, terminal 131, brush 117, uppercontact of-sequence switch spring 132, upper right-hand winding-otrepeating coil 135, to ground. Relay 253 closes a locking circuit foritself from grounded battery, left-hand contact of sequence switchspring 252, winding of relay 253, lower contact of sequence switchspring 255, armature and front contact of relay 253, conductor 256,upper contact of sequence switch spring 218, lefthand winding of relay219, upper and lower right-hand contacts of sequence switch spring 220,to ground. Relay 219 becomes energized and closes a locking circuit foritself from grounded battery, right-hand winding of relay 219, lowercontact of sequence switch spring 221, right-hand armature and frontcontact of relay 219, lower contact of sequence switch spring 244 toground. Relay 219 also closes a circuit from grounded battery, lowercontact of sequence switch spring 258, winding of relay 259, right-handarmature and front contact of relay 219, lower contact of sequenceswitch spring 244, to ground. Relay 259 completes a circuit fromgrounded battery, resistance 262. left-hand armature and front contactof relay 259, winding of relay 202, lower lett-hand contact of sequenceswitch spring 230, to ground. Relay 202 becomes energized and completesa circuit from grounded battery, power magnet of sequence switch 200,upper left-hand contact ot1 sequence switch spring 211, right-handarmature and front contact of relay 202,'to ground, :tor moving thesequence switch 200 out of position 10 and into position 12.

As soon as sequence switches 200 and 300 reach positions 11 and 7,respectively, a. circuit is closed from grounded battery, winding otrelay 304, lower left-hand contact ot sequence switch spring 305,conductor 306, terminal 243. brush 225, conductor 249, lower contact ofsequence switch spring 250, upper armature and back contact of relay260, upper right-hand winding of repeating coil 254. to ground. Relay304 by attracting its lett-hand armature completes a circuit for movingthe sequence switch 300 out of position 7 and into position 8, thiscircuit being traced from grounded battery, power magnet of sequenceswitch 300, lower and upper fight-hand contacts of sequence switchspring 308, left-hand armature and front contact of relay 304, toground.

It will first be assumed that the called line is idle and a high batterypotential will then be found upon the test terminal 328. As soon as thesequence switch 300 reaches position 8, a circuit is closed fromgrounded battery, winding of cutoi relay 331, terminal 328, brush 315,contact ot' sequence switch spring 332, left-hand low resistance windingof relay 333, lower contacts of sequence switch spring 334, righthand`high resistance winding of relay 333, to ground. Relay 333 becomesenergized and completes a. locking circuit for itself, this circuitbeing traced through its lefthand low resistance winding and itslefthand armature and front contact, to ground. T his circuit shunts outthe high resistance of winding of relay 333 and so reduces the potentialon the terminal 328 as to cause the line to test busy. The energizationof relay 333 also closes `a circuit from grounded battery, power magnetof sequence switch 300, lower left-hand contact of sequence switchspring 311, right-hand armature and front contact of relay 333, toground, for moving the sequence switch 300 out of position 8 and intoposition 10. As soon as the sequence switch 300 leaves position 7-1/4,the relay 304 denergizes so that the sequence switch 300 is immediatelymoved out of position 10 and into position 14, due to a circuit beingclosed from grounded battery, power magnet of sequence switch 300, lowerright-hand and upper lett-hand contacts of sequence switch spring 308,lefthand armature and back contact of relay 304, to ground. Sequenceswitch 300 is moved out of position 14 and into position 16, due to thecircuit previously described, for moving it out of position 8. Inposition 16, the line conductors 306 and 301 are extended through to thecalled line.

As soon as the sequence switch 200 reaches position 11 when moving fromposition 10 to position 12 in the manner above described, the relay 253is held energized over a circuit traceable from grounded battery, uppercontact of sequence switch spring 261, lett-hand armature and frontcontact of relay 202, lower right-hand contact of sequence switch spring252, winding of relay 253, upper left-hand winding of repeating coil254, conductor 205, terminal 131, brush 117, upper contact of sequenceswitch spring 132, upper right-hand winding of repeating coil 135 toground. In position 11, the relay 253l completes a circuit from groundedbattery, upper contact ot sequence switch spring 255, armature and frontcontact of relay 253, upper contact of sequence switch spring 258,winding of relay 259, upper left-hand contact of sequence switch spring244, to ground. This circuit is maintained energized until the sequenceswitch 200 leaves position 14. Relay 259, by holding its lett-handarmature attracted, still maintains the circuit for relay 202 closed.

It will be assumed that the commutator brush 233 is in engagement withan insulated segment. ot' the commutator 263, when the sequence switch200 reaches position 12. A circuit will then be closed from` groundedbattery, upper contact of sequence switch spring 255, armature and frontcontact of relay 253, upper contacts of sequence switch spring 258,winding of relay 260, armature and back Contact of relay 264, armatureand back contact of relay 265, left-hand armature and back Contact ofrelay 219, to ground. Relay 260 becomes energized and connects ringingcurrent to the called line over a circuit from grounded sourcev ofringing current, left-hand winding of relay 265, lefthand Contact ofsequence switch spring 266, lower armature and front contact of relay260, left-hand contact of sequence switch Spring 247, conductor 248,brush 224, terminal 242, conductor 301, lower contacts of sequenceswitch spring 302, brush 316, terminal 329, apparatus of substation B,terminal 330, lbrush 317, upper contact of sen quence switch spring 305,conductor 306, terminal 243, brushf 225, conductor 249, lower contact ofsequence switch spring 250, upper armature and front contact of relay260, to ground.

Relay '265 does not become energized at this time due to the highresistance in the circuit at the substation B. Ringing current is rthusapplied to the called line until the called party answers, at which timerelay 265 receives suiiicient current and attracts the armature. Acircuit is then closed rthrough the winding of relay 264,v which hadpreviously been shunted out by the circuit through the armature and backcontact of relay 265 and the armature and back Contact of the relay 264.Relay 264 by attracting its armature closes a locking circuit for itselfand places a shunt around relry 260. Relay 260 denergizes and connectsthe subscribers lines together for conversa-tion.

The operator now depresses the listening out key 179, provided she hasnot previously done so, which completes a circuit from grounded battery,power magnet of sequence switch 175, upper contact of sequence switchspring 177, key 179 to ground, for moving the sequence switch 175 intoposition 8, which is the listening out position.

As soo-n as the subscribers are through talking and have replaced theirreceivers, the operator receives a disconnect signal in the well-knownmanner. She then removes plug 104 from jack 105. Relay 106 denergizesand completes a circuit from grounded battery, power magnet of sequenceswitch 175, lower contact of sequence switch sprlng 177, armature andback contact of relay 106 to ground, for moving the sequence switch 175out of position 8 and into position 1. Y

-The denergization of relay 106 also closes a circuit from groundedbattery, power magnet of sequence switch 100, upper right-hand contactof sequence switch spring 107, armature and back Contact of relay 106 toground, for Ind-ving the sequence switch 100 out of position 16 and intoposition 18. 1n position 18, a circuit is completed from groundedbattery, winding of downdrive magnet 138,-lower contact of sequenceswitch spring 112 to' ground. Under the control of the downdrive magnet138, the brush Upd 116 is returnedto its normal position. As soon as thecommutator brush 120 reaches its normal position, a circuit is completedfrom grounded battery, power magnet of sequence switch 100, upperright-hand contact of sequence switch spring 113, conducting segment139, commutator brush 120 to ground, for moving the sequence switch 100lout of position 18 and into position 1.

As soon as the sequence switch 100 leaves position 16, the holding'circuit of relay 253 is opened at the upper left-hand contact ofsequence switch spring 132. Relay 253 by retracting its armature opensthe circuit of relay 259, which denergizes, and opens the circuit ofrelay 202. Relay 202 by retracting its rightlhand armature closes acircuit from grounded battery, power magnet of sequence switch 200,upper right-hand contact of sequence switch spring 211, righthandarmature and back contact of rela-y 202 to ground, moving the sequenceswitch out of position 12 through position 14 and into position 18. lnposition 18, a circuit is completed from grounded battery, winding ofdowndrive magnet 271, lower contact of sequence switch spring 215 toground. 'Under the control of the dowvndrive magnet 217, the brush rod236 is returned to its normal position. As soon as the commutator brush234 'reaches its normal position, a Circuit is completed from groundedbattery, power magnet of sequence switch 200, lower contact of sequenceswitch spring 275, conducting segment 276, commutator brush 234,

lower contact of sequence switch spring 220 to ground, for moving thesequence switch 200 out of position 18 and into position 1.

As soon as the sequence switch 200 leaves position 16, the holdingcircuit of relay 307 is opened at the lower contact of the sequenceswitch spring 244. Relay 307 by retracting its left-hand armaturecompletes. a circuit from grounded battery, power magnet of sequenceswitch 300, upper left-hand contact inea-,aes

of sequence switch 311, left-hand armature and back contact of relay 307to ground, for moving the sequence switch'out of position 16, throughposition 17 and into position 1'8. A circuit is then closed fromgrounded battery, winding of downdrive magnet 340, lower contact ofsequence switch spring 341 .to ground. Under control of the downdrivecontact of sequence switch spring 323 to ground, for moving the sequenceswitch-300 out of position 18 and into position 1.

1f the called line is busy when the sequence switch 300 reaches position8, the test relay 333 does not receive suiiicient current to attract itsarmatures, due to the low potential on the test terminal 328. Relay 304,however, is energized in thisrcase in position 8, due to a circuit beingclosed (from grounded battery, winding of relay 304, lower contacts ofsequence switch spring 337, left-hand armature and back contact or'relay 338, right-hand armature and back contact of relay 333 to ground.Relay 304 by attracting its left-hand armature completes a circuit fromgrounded battery, power magnet of sequence switch 300, lower and upperrighthand contacts of sequence switch spring 308, left-hand armature andfront contact of relay 304 to ground, for moving the sequence switch 300out of position 8 and into position 10. As soon as the sequence switchreaches position 9, a circuit `is closed from grounded battery, windingof relay 338, upper contacts of sequence switch Spring 339 to ground.The energization oi? relay 338 opens the circuit of relay 304,whichvdenergizes and completes a circuit for moving the sequence switch300 out of position 10 and into position 14, this circuit being tracedfrom grounded battery, power magnet of sequence switch 300, lowerright-V hand and upper left-hand contacts of sequence switch spring308,1eft-hand armature and back contact of relay 304 to ground'. Inposition 14, a circuit is completed for the downdrive magnet 340, fromgrounded battery, winding of downdrive magnet 340, upper contact ofsequence switch spring 341, right-hand armature and back Contact ofrelay 333 to ground. Under the control of the downdrive magnet 340, thebrush shaft 342 isreturned to its normal position. As soon as thecommutator brush 320 engages the normal conducting segment 343, acircuit is closed from grounded battery, power magnet of sequence switch300, lower righthand contact of sequence switch spring 311, conductor344, conducting segment 343, brush 320, lower contact of sequence switchspring 323 to ground, for moving the sequence switch 300 out of position14 and into position 17 A busy tone is now connected to the lower lineconductor 301 through the upper contacts of sequence switch spring 334.The operator receives a characteristic flash of the so-calledsupervisory lamp (not shown) in a well-knownnianner and removes plug 104from the jack 105, thereby causing the denergization of relay 106. Theswitches are then returned to their normal positions in the same manneras above described. 1

We will nowconsider the wipe-out operation which may take place inposition 11 of sequence switch 100. It will be remembered that thesequence switch 400 is in position 8 at this time. It will also beobserved that the wipe-out operation can only take place while thesequence switch 175 is in position 5. When the wipe-out key 173 isoperated, a circuit is completed from grounded battery, winding of relay140, upper contact of sequence switch spring 174, Wipe-out key 173 toground. In position 11 of the sequence switch 100, relay 140 completes avcircuit from grounded battery, winding of relay 421, brush 440,terminal 441, conductor 442, contact of sequence switch spring 144,armature and front contact of relay 140 to ground. Relay 421 byattracting its left-hand armature completes a locking circuit for itselffrom grounded battery, winding of relay 421, left-hand armature andfront contact of relay 421, upper contact of sequence switch spring 435,lower contact of sequence switch spring 484 to round. Relay 421 byattracting its rightand armature opens the fundamental circuit throughthe stepping relay 494 and closes it through the right-hand winding ofthe relay 436. In this manner the switch being operated is removed fromthc control of the counting relays. Assuming that the brushes 117, 118and 119 have just engaged the terminals 131, 130 and 127, respectively,at the time the wipe-out key 173 is operated. Sequence switch 200 willmove into position 2 in the same manner as above described, causing thefundamental circuit to be closed in the same manner as above describedexcept that it will be completed through the right-hand winding of relay436 instead of through the winding of stepping relay 494 and the outerarmature and back contact of the counting relay 0. Relay 436 will not,however, be energized at this time due to the high resistance of thewinding 202. In position 2 of the sequence switch 200, the above tracedcircuit of the updrivc magnet 217 will be completed. Under the controlof this updrive magnet, the brush rod 236 'tion 7, due to a circuitbeing closed from grounded battery, power magnet o-f sequence switch200, lower contacts'of sequence switch spring 214, left-hand armatureand back contact of relay 219 to ground. The sequence switch 200 ismoved out of position 7 through positions 8 and 9 and into position 10,due to the circuit above described for movlng it out of position 2. Inposition 10, a circuit is completed from grounded battery, lower contactof sequence switch spring 208, winding of relay 209, upper contact ofsequence switch spring 210, over-How contact 277, commutator brush 234,lower contact of sequence switch spring 220 to ground. Relay 209completes a circuit from grounded battery, left-hand contact of sequenceswitch 4,spring 252, winding of relay 253, upper lefthand winding ofrepeating. coil 254, conductor 205, terminal 131, brush 117, lowercontact of sequence switch spring 132, conductor 111, terminal 419,brush 420, righthand armature and front contact of relay 421, right-handwinding of relay 436, brush 422, terminal 423, conductor 424, uppercontact of sequence switch spring 133, brush' 118, terminal 130,conductor 206, upper contact of sequence switch spring 279, armature andfront contact of relay 209, lowercontact of sequence switch spring 212to ground. Relay 436 now receives sufficient current to attract itsarmatures and completes a locking circuit for itself from groundedbattery, left-hand winding of relay 436, left-hand armature and frontcontact of relay 436, lower contact of sequence switch spring 435, lowercontact of sequence switch spring 484 to ground. Relay 436 alsocompletes a circuit from grounded battery, power magnet of sequenceswitch 490, upper left-hand contact of sequence switch spring 492,righthand armature and front contact of relay 436 to ground, .for movingthe sequence switch 490 into its normal position. As soon as thesequence switch 490 reaches position 1, the cord finder is released andthe sequence switch 100 moved into position 16 in the same manner asabove described.

The energization of relay 253 ciuses the sequence switch 200 to moveinto position 12 in the same manner as above described. As

soon as theroperator removes the'plug 104e rom'the jaclr 105, thesequence switches 100 and 200 are moved into their normal positions inthe same manner as above described.

It the wipe-out key is operated while the sequence switch 200 is inposition 3, it conleading to Aa iinal selector is seized in the samemanner as above described and the ifundamental circuit is completed,causing the energization of relay 304i which moves the sequence switch300 into position 2. IThe relay 4.36 does not attract its armatures atthis time, due to the high resistances of the winding of relay 304, andof the resistance 303. Due to the energization of relay 304, the circuitfor the updrive magnet 312 will be closed, thereby causing the brushesto move upward until the commutator brush 320 engages the overow contact350. A circuit is then completed trom grounded battery, power ymagnet ofsequence switch 300, lower right-hand contact of sequence switch spring351, overow contact 350, commuy tator brush 320, lower contact ofsequence switch spring 323 to ground, for moving the sequence switch outoi position 2 and into position 10. As soon as the sequence switch 300leaves position 6, the sequencevswitch 200 is moved out of position 9and into position 10 in the manner above described. Relay 304 isdenergized in position 10 in the saine manner las above described, sothat the sequence switch 300'is immediately moved out of position l0 andinto position 14, due to a circuit from grounded battery, power magnetof sequence switch 300, lower right and upper lett-hand contacts ofsequence switch spring 308, left-hand armature and back contact of relay304 to ground. Sequence switch 300 is immediately moved out of positionlei and into position 16, due to the circuit which moved it out ofposition 2. As soon as the sequence switch 300 reaches fposition 16, a.circuit is closed or the relay 209, from grounded battery, lower contactot sequence switch spring 208, winding of relay 209, upper contact ofsequence switch spring 210, upper righthand Contact of sequence switchspring 250, conductor 249,

Y f brush 225,ter1ninal 243, conductor 30S, lower right-hand contact'ofsequence switch springl 305, lower left-hand contact oi sequencenosas-ce switch spring 351, overow contact 350, o3

leased in the manner above described. It V the wipe-out key is depressedwhile the sequence switch 300 is in position between 2 and 7,'it isobvious that the brushes ofthe final selector will be moved upward untilthe overflow contact is reached, whereupon the connection will bereleased in the manner similar to that -just described.

vWhat isclaimed is: Y v I 1. ln aV telephone exchange system, a switch,sending apparatus, means to operate said switch in a motion controlledby said sending apparatus, means operative during said motion torender-said sender control inedective and to allow said motion tocontinue until a limiting position is reached, and means made operativelwhen said limiting position is reached for releasing said switch.

2. ln a telephone exchange system, a train of switches, sendingapparatus, means to operate each of said switches in a motion controlledby said sending apparatus, means operative during any one of saidmotions to render said sender control inedective and to allow the motionofA the switch being operated to continue until a limiting position isreached, and means made operative when said limiting'position is reachedfor releasing said switch and the switches previously controlled by saidsending apparatus.

3. In a telephone exchange' system, a train of switches, sendingapparatus, means to operate each of said switches in a motion controlledby said sending apparatus, a wipeout key, means controlled Aby said keywhen operated during any one of said motions for rendering said sendercontrol ine'ective and to allow the motion of the switch being operatedto continue until a limiting position is reached, and means madeoperative when said limiting position is reached for releasing saidswitch and the switches previously controlled by said sending apparatus.

4. In a telephone exchange system, a train of switches, a controlcircuit therefor, sending apparatus arranged to be included in saidcontrol circuit, means controlled by said circuit for operating each ofsaid switches in a motion controlled by said sending apparatus, meansoperative during any one of said motions to disconnect said sending ap.

paratus from lsaid circuit and to maintain said circuit closed to allowthe motionof the. switch being operated to continue until a limitingposition is reached, and mea-ns made operative when said limitingposition is reached for releasing said switch and the rool switchespreviously controlled by said Sending apparatus.

5. In a telephone exchange system, a train of switches, a controlcircuit therefor, sending apparatus arranged to be included in saidcontrol circuit, means controlled by said circuit for operating each ofsaid switches in a motion controlled by said sending apparatus, amarginal relay, a {wipe-out key, a relay operative by the depression ofsaid key during any one of said motions todisconnect said Sendingapparatus from said circuit and to maintain said control circuit closedto allow the motion of the switch being controlled to continue until alimiting position is reached, an energizing circuit for said marginalrelay completed when said limiting position is reached, and meansoperative by said marginal relay energizing for releasing said switchand the switches previously controlled by said sending apparatus.

6. In a telephone system, a switch, a control circuit therefor, sendinapparatus arranged to be included in saic control circuit, meanscontrolled by said circuit for operating said switch ina motioncontrolled by said sending apparatus, means operative during said motionfor disconnecting said sending apparatus from said circuit and formaintaining said circuit closed to allow said motion to continue untilalimiting position is reached, and means made operative when saidlimiting position is reached for releasing said switch.

7. In a telephone exchange system, a calling line, a connecting circuitterminating in a selector switch, means for connecting said calling lineto said lconnecting circuit, a called line, a plurality of switches,sending apparatus, means for operating each of =said plurality ofswitches successively in a motion controlled by said sending apparatusto extend a connection from said selector switch to said called line,means operative during any one of said movements to render said sendercontrol ineffective and to allow ALBEN E. LUNDELL. FRANKLIN A. STEARN.

